openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/drivers/scsi/sr.h b/drivers/scsi/sr.h
new file mode 100644
index 000000000..2d92f9cb6
--- /dev/null
+++ b/drivers/scsi/sr.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *      sr.h by David Giller
+ *      CD-ROM disk driver header file
+ *      
+ *      adapted from:
+ *      sd.h Copyright (C) 1992 Drew Eckhardt 
+ *      SCSI disk driver header file by
+ *              Drew Eckhardt 
+ *
+ *      <drew@colorado.edu>
+ *
+ *       Modified by Eric Youngdale eric@andante.org to
+ *       add scatter-gather, multiple outstanding request, and other
+ *       enhancements.
+ */
+
+#ifndef _SR_H
+#define _SR_H
+
+#include <linux/mutex.h>
+
+#define MAX_RETRIES	3
+#define SR_TIMEOUT	(30 * HZ)
+
+struct scsi_device;
+
+/* The CDROM is fairly slow, so we need a little extra time */
+/* In fact, it is very slow if it has to spin up first */
+#define IOCTL_TIMEOUT 30*HZ
+
+
+typedef struct scsi_cd {
+	unsigned capacity;	/* size in blocks                       */
+	struct scsi_device *device;
+	unsigned int vendor;	/* vendor code, see sr_vendor.c         */
+	unsigned long ms_offset;	/* for reading multisession-CD's        */
+	unsigned use:1;		/* is this device still supportable     */
+	unsigned xa_flag:1;	/* CD has XA sectors ? */
+	unsigned readcd_known:1;	/* drive supports READ_CD (0xbe) */
+	unsigned readcd_cdda:1;	/* reading audio data using READ_CD */
+	unsigned media_present:1;	/* media is present */
+
+	/* GET_EVENT spurious event handling, blk layer guarantees exclusion */
+	int tur_mismatch;		/* nr of get_event TUR mismatches */
+	bool tur_changed:1;		/* changed according to TUR */
+	bool get_event_changed:1;	/* changed according to GET_EVENT */
+	bool ignore_get_event:1;	/* GET_EVENT is unreliable, use TUR */
+
+	struct cdrom_device_info cdi;
+	struct mutex lock;
+	struct gendisk *disk;
+} Scsi_CD;
+
+#define sr_printk(prefix, cd, fmt, a...) \
+	sdev_prefix_printk(prefix, (cd)->device, (cd)->cdi.name, fmt, ##a)
+
+int sr_do_ioctl(Scsi_CD *, struct packet_command *);
+
+int sr_lock_door(struct cdrom_device_info *, int);
+int sr_tray_move(struct cdrom_device_info *, int);
+int sr_drive_status(struct cdrom_device_info *, int);
+int sr_disk_status(struct cdrom_device_info *);
+int sr_get_last_session(struct cdrom_device_info *, struct cdrom_multisession *);
+int sr_get_mcn(struct cdrom_device_info *, struct cdrom_mcn *);
+int sr_reset(struct cdrom_device_info *);
+int sr_select_speed(struct cdrom_device_info *cdi, unsigned long speed);
+int sr_audio_ioctl(struct cdrom_device_info *, unsigned int, void *);
+
+int sr_is_xa(Scsi_CD *);
+
+/* sr_vendor.c */
+void sr_vendor_init(Scsi_CD *);
+int sr_cd_check(struct cdrom_device_info *);
+int sr_set_blocklength(Scsi_CD *, int blocklength);
+
+#endif